| // Ceres Solver - A fast non-linear least squares minimizer |
| // Copyright 2017 Google Inc. All rights reserved. |
| // http://ceres-solver.org/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are met: |
| // |
| // * Redistributions of source code must retain the above copyright notice, |
| // this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above copyright notice, |
| // this list of conditions and the following disclaimer in the documentation |
| // and/or other materials provided with the distribution. |
| // * Neither the name of Google Inc. nor the names of its contributors may be |
| // used to endorse or promote products derived from this software without |
| // specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| // POSSIBILITY OF SUCH DAMAGE. |
| // |
| // Author: yp@photonscore.de (Yury Prokazov) |
| |
| #ifndef CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ |
| #define CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ |
| |
| #include "ceres/concurrent_queue.h" |
| #include "ceres/internal/config.h" |
| #include "ceres/internal/export.h" |
| |
| namespace ceres::internal { |
| |
| // Helper for C++ thread number identification that is similar to |
| // omp_get_thread_num() behaviour. This is necessary to support C++ |
| // threading with a sequential thread id. This is used to access preallocated |
| // resources in the parallelized code parts. The sequence of tokens varies from |
| // 0 to num_threads - 1 that can be acquired to identify the thread in a thread |
| // pool. |
| // |
| // |
| // Example usage pseudocode: |
| // |
| // ThreadTokenProvider ttp(N); // allocate N tokens |
| // Spawn N threads { |
| // int token = ttp.Acquire(); // get unique token |
| // ... |
| // ... use token to access resources bound to the thread |
| // ... |
| // ttp.Release(token); // return token to the pool |
| // } |
| // |
| class CERES_NO_EXPORT ThreadTokenProvider { |
| public: |
| explicit ThreadTokenProvider(int num_threads); |
| |
| // Returns the first token from the queue. The acquired value must be |
| // given back by Release(). |
| int Acquire(); |
| |
| // Makes previously acquired token available for other threads. |
| void Release(int thread_id); |
| |
| private: |
| // This queue initially holds a sequence from 0..num_threads-1. Every |
| // Acquire() call the first number is removed from here. When the token is not |
| // needed anymore it shall be given back with corresponding Release() |
| // call. This concurrent queue is more expensive than TBB's version, so you |
| // should not acquire the thread ID on every for loop iteration. |
| ConcurrentQueue<int> pool_; |
| ThreadTokenProvider(ThreadTokenProvider&) = delete; |
| ThreadTokenProvider& operator=(ThreadTokenProvider&) = delete; |
| }; |
| |
| } // namespace ceres::internal |
| |
| #endif // CERES_INTERNAL_THREAD_TOKEN_PROVIDER_H_ |